1. Field of Invention
The invention relates to the field of engines and methods of manufacturing engines and more particularly to an engine, and a method of making the engine, that allows for a number of engines of varying horsepower outputs to be manufactured from a relatively small number of basic engine components.
2. Description of the Related Art
Internal combustion engines are known in the art. Various methods of manufacturing such internal combustion engines have been devised and disclosed.
Some have tried to streamline and improve the process of manufacturing internal combustion engines. For example, U.S. Pat. No. 4,622,864 to Fetouh purports to disclose a reciprocating piston engine including a modular power transmission sub-assembly. The invention purports to provide a lightweight and low-cost engine construction.
U.S. Pat. No. 3,941,114 to Seifert purports to disclose a cylinder crankcase for a multi-cylinder internal combustion engine in which the crankcase consists of welded-together cast housing elements that are connected in series in a building-block-like matter.
U.S. Pat. No. 5,456,076 to Zornes discloses an external heat source engine that includes a telescopic crankcase structure. The engine structure may be constructed so that two or more sub-systems are housed in one or more modules according to the specification of the patent. Two or more power modules may then be coupled together and engine power and speed control may be obtained by varying the relative phase angle of the couple.
U.S. Pat. No. 4,676,205 to Kaufman purports to disclose and arrangement for mounting a two-stroke cycle vertical crankshaft internal combustion engine onto a rotary mower deck to accept a four-stroke cycle vertical crankshaft internal combustion engine whereby either type of engine may be adapted to the same mower deck.
U.S. Pat. No. 4,610,228 to Fink et al. purports to disclose a crankcase assembly for an engine to be mounted to and associated with a portable tool such as a chain saw. A plastic crankcase is connected to the cylinder of the engine and an annular insulating member is mounted between the cylinder and the crankcase.
In light of the prior art, the possibility for improvements still remain and are desirable for improving the efficiency and cost of the manufacturing process for engines, and especially smaller horsepower internal combustion engines such as might be used in the lawn care industry. In this industry, for smaller lawn care products, a large percentage of the product cost is due to the cost of the engine itself. For example, as of the date of filing this patent application, it is not uncommon for some walk behind lawn mowers to cost less than $100 even though those walk-behind lawn mowers are provided with an internal combustion engine of five horsepower or more. With cost pressure keeping the retail price of this product low, it is important that improvements in the efficiencies in the manufacture and design of the engine itself be made in order to provide adequate profit to the manufacturer of the lawn mower.
According to one aspect of the present invention, a method of providing a family of engines so that greater manufacturing efficiencies are obtainable is disclosed. The invention provides a modular engine design system for designing a family of engines. The engines in the family of engines provide for a variety of power outputs to be achieved without major redesigning of engine components. Each engine comprises at least one cylinder block defining a cylinder therein, a crankcase having an opening therein communicating with the cylinder, a piston adapted for reciprocal movement in the cylinder, a crankshaft adapted for rotational movement within the crankcase, a connecting rod interconnecting the piston and the crankshaft, and a camshaft for controlling the intake valve and exhaust valve assembly.
In accordance with the invention, the modular engine design system provides a basic engine design capable of generating a first range of power output. For illustrative purposes only, and not by way of limiting the present invention, the basic engine, for example, may be capable of generating about 3.5 to 4.5 horsepower, inclusive. The basic engine design utilizes basic engine components, designated by the letter A, which include: a first cylinder block (A) defining a first cylinder (A) of first predetermined dimensions, a first crankcase (A), a first piston (A), a first crankshaft (A), a first connecting rod (A) of length L1, and a first camshaft (A).
In accordance with the invention, the modular engine design system provides a second engine design for providing a second engine capable of generating a second range of power output, greater than the power output of the basic engine. The modular engine design system utilizes a plurality of engine components that are substantially structurally identical to the basic engine components in order to achieve the desired power output range. For ease of illustration, different alphabetic labels will identify engine components that differ structurally from the basic engine components.
The second engine design may, for example, provide an engine capable of generating about 5.0 to 6.5 horsepower. This second engine design would utilize a plurality of the basic engine components. For example, the second engine design might utilized a first cylinder block (A), defining a cylinder (A) having the same predetermined dimensions, a first piston (A), a first crankcase (A), and a first camshaft (A) are basic engine components utilized in the second engine design.
However, in the inventive engine design system, several of the basic components are selectively replaceable with modified components. For instance, in the exemplary second engine design, the first connecting rod (A) is selectively replaced with a second connecting rod (B), having a length L2. Likewise, first crankshaft (A) is selectively replaced by second crankshaft (B). In this example, L2 is less than L1. The power output is directly related to the amount of displacement, or piston stroke, of the piston within the cylinder. In a cylinder of predetermined diameter, a longer stroke correlates to a greater cylinder volume, and a shorter stroke correlates to a lesser cylinder volume. A shorter connecting rod allows for a longer stroke within cylinders of the same predetermined dimensions, and hence more power. Therefore, in the modular engine design system of the present invention, changes in the length of the connecting rod, while keeping the cylinder/piston dimensions the same, provide for the changes in power output from the basic engine to the second engine in the family of engine designs.
The modular engine design system utilizes several common engine-building components that are adapted to be used with modified engine components to provide a family of engines of varying power outputs. Therefore, in the modular engine design system, greater manufacturing efficiencies can be achieved.
In accordance with yet another feature of the invention, a third engine design is provided. The third engine design utilizes a third crankshaft (C) adapted to receive two first connecting rods (A, A), each having a length L1, which are operatively connected to two first pistons (A, A). This third engine design utilizes two of the first cylinder blocks (A, A), each of which define a first cylinder (A) of first predetermined dimensions. A modified crankcase (B) is provided which has one opening that communicates with one of the cylinders and a second opening that communicates with the second cylinder. A modified camshaft (B) is also provided to operate the valve assemblies associated with each cylinder/piston combination.
In accordance with yet another feature of the invention, a fourth engine having a power output greater than the basic engine is provided through a fourth engine design. Again, a plurality of basic engine components is utilized. For example, the fourth engine design utilizes a fourth crankshaft (D) adapted to receive two of the second connecting rods (B, B), each having a length L2, which are operatively connected to two first pistons (A, A). The fourth engine design utilizes two of the first cylinder blocks (A, A), and the modified crankcase (B), as above. This fourth engine design utilizes the modified camshaft (B).
The second engine design differs from the basic engine design mainly by differing the stroke length of the piston. The third engine design differs from the basic engine design mainly by the addition of a second cylinder/piston combination. The fourth engine design differs from the basic engine design by combining the change in stroke length of the piston with the addition of a second cylinder/piston combination. Each engine design in associated with its own crankshaft to accommodate the different stroke lengths of the pistons and/or the number of pistons.
This concept of a modular engine design system that provides for a related series of engines is extended further in the present invention by providing a second series of engine designs. The second series of engine designs utilizes a common engine design scheme with the first series of engines. Therefore, the same modular concepts are used to create another family of related engines. The basic engine design of the second series utilizes a modified cylinder block (B) defining a modified cylinder (B) of predetermined dimensions greater than the dimensions of the first cylinder. The change in cylinder size provides a series of engine designs capable of providing engines with greater power output than the corresponding engines in the first series. An enlarged piston (B) is adapted for reciprocal movement within the modified cylinder (B) and is connected to another modified crankshaft (D) by a modified connecting rod (C) having length L3. A modified crankcase (C) has an opening therein adapted for communicating with the modified cylinder (B). This particular engine design utilizes yet another modified camshaft (C).
The present invention is further directed to modifications in the design of the basic engine of the second series corresponding to the changes in the design of the basic engine of the first series. As in the first series, other engines in this second series are produced by utilizing a connecting rod (D) having a length L4 less than L3. Additional engines in this family are provided by utilizing a second cylinder/piston combination with shorter or longer connecting rods. As in the first series of engine designs, modifications to the crankshaft, crankcase and camshaft are also provided.
In accordance with the present invention, there is provided a method of providing a family of engines sharing a common engine design scheme. The method comprises the steps of providing a first engine design for a basic engine having a first power output. The first engine is formed of basic engine components including a first cylinder block, a first crankcase, a first piston, a first crankshaft, a first connecting rod, and a first camshaft. The method further comprises the step of providing a second engine design for a second engine related to the first engine wherein at least one of the basic engine components is selectively replaced with a corresponding modified engine component substantially different from the replaced basic engine component. In that way, the second engine is associated with a power output substantially different from the first power output.
According to another aspect of the invention, a common engine design scheme is adapted to utilize a second cylinder block rather than the first cylinder block. Corresponding engine parts are therefore selectively replaced for use with the second cylinder block.
According to a further aspect of the invention, an engine having a first power output rating includes a crankcase that has first and second substantially symmetrical portions.
According to a further aspect of the invention, the first engine includes a piston that is received for reciprocal movement within a cylinder along a piston axis, the engine including a crankcase that is divided into first and second portions along a plane that is angled relative to the piston axis.
According to a further aspect of the invention, the engine includes a piston that is received for reciprocal movement with a cylinder along a piston axis, the engine including a crankcase that is divided into first and second portions along a plane that is substantially perpendicular to the piston axis.
One object of the invention is to provide an internal combustion engine for the generation of power.
Another object of the invention is to provide an internal combustion engine specifically adapted for smaller horsepower applications, such as lawn care products, such as lawn mowers, riding lawn mowers, snow throwers, tillers, and the like.
Another object of the invention is to provide engines of varying horsepower generating capabilities that can be efficiently and inexpensively manufactured.
Another object of the invention is to provide a family of engines related by use of common engine components.
Another object of the invention is to provide first and second series of engines utilizing similar design modifications between family members in each series.
Another object of the invention is to provide a business method whereby internal combustion engines of varying horsepower generating capabilities may be more efficiently produced.
One advantage of the present invention is that engines with a wide range of power outputs can be easily provided by selective replacement of basic engine components with modified engine components.
Other benefits flowing from the invention are reduced inventory costs and reduced manufacturing costs.
Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.